This invention relates to novel hydroxy-peroxides of the Structure A: EQU HO--R.sub.11 --X--OO--R (A)
[wherein R--, --R.sub.11 -- and --X-- are as defined in the Summary of the Invention Section] having 10 hour half-life temperatures of 85.degree.-110.degree. C., the processes for their preparation, and the use of these novel compositions in curing of unsaturated polyester resins and in initiating polymerization of ethylenically unsaturated monomers.